date_default_timezone_set('PRC');

$last_week_first = strtotime(date('Y-m-01', strtotime('-1 week')));
$last_week_last =  strtotime(date('Y-m-d',$last_week_first)."+1 week -1 day");

$last_month_first = strtotime(date('Y-m-01', strtotime('-1 month')));
$last_month_last =  strtotime(date('Y-m-d',$last_month_first
 
)."+1 month -1 day");

$last_half_first = strtotime(date('Y-06-01', strtotime('-6 month')));
$last_half_last =  strtotime(date('Y-m-d',$last_half_first)."+6 month -1 day");

$last_year_first = strtotime(date('Y-01-01', strtotime('-1 year')));
$last_year_last =  strtotime(date('Y-m-d',$last_year_first)."+12 month -1 day"
 
);

echo date('Y-m-d',$last_week_first);
echo '<br />';
echo date('Y-m-d',$last_week_last);
echo '<br />';
echo date('Y-m-d',$last_month_first);
echo '<br />';
echo date('Y-m-d',$last_month_last);
echo '<br />';
echo date('Y-m-d',$last_half_first);
echo '<br />';
echo date('Y-m-d'
 
,$last_half_last);
echo '<br />';
echo date('Y-m-d',$last_year_first);
echo '<br />';
echo date('Y-m-d',$last_year_last);

注 : 時間不包含當天，因為只獲取到00:00，如果需要包含當天請把 -1 day 刪除，包含當天，但多一秒